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Phosphorus Fractionation Responds to Dynamic Redox Conditions in a Humid Tropical Forest Soil
Author(s) -
Lin Yang,
Bhattacharyya Amrita,
Campbell Ashley N.,
Nico Peter S.,
PettRidge Jennifer,
Silver Whendee L.
Publication year - 2018
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2018jg004420
Subject(s) - redox , anoxic waters , ammonium oxalate , chemistry , oxalate , environmental chemistry , phosphorus , soil water , ammonium , fractionation , inorganic chemistry , soil science , geology , chromatography , organic chemistry
Phosphorus (P) is a key limiting nutrient in highly weathered soils of humid tropical forests. A large proportion of P in these soils is bound to redox‐sensitive iron (Fe) minerals; however, little is known about how Fe redox interactions affect soil P cycling. In an incubation experiment, we changed bulk soil redox regimes by varying headspace conditions (air versus N 2 gas) and examined the responses of soil P and Fe species to two fluctuating treatments (4‐ or 8‐day oxic followed by 4‐day anoxic) and two static redox treatments (oxic and anoxic). A static anoxic headspace increased NaOH‐extractable inorganic P and ammonium oxalate‐extractable total P (AO‐P t ) by 10% and 38%, respectively, relative to a static oxic headspace. Persistent anoxia also increased NaHCO 3 ‐extractable total P (NaHCO 3 ‐P t ) toward the end of the experiment. Effects of redox fluctuation were more complex and dependent on temporal scales. Ammonium oxalate‐extractable Fe and P t concentrations responded to redox fluctuation early in the experiment, but not thereafter, suggesting a depletion of reductant over time. Immediately following a switch from an oxic to anoxic headspace, concentrations of AO‐P t , AO‐Fe, and HCl‐extractable Fe(II) increased (within 30 min) but fell back to initial levels by 180 min. Surprisingly, the labile P pool (NaHCO 3 ‐P t ) decreased immediately after reduction events, potentially due to resorption and microbial uptake. Overall, our data demonstrate that P fractions can respond rapidly to changes in soil redox conditions, and in environments where redox oscillation is common, roots and microbes may benefit from these rapid P dynamics.